The present invention generally relates to motion systems and in particular to a system and method for stabilizing a stage of a linear motion system during high precision positioning.
Typically, linear motion systems comprise one or more tracks or guide rails on which a stage or carriage is moved. The movement can be accomplished by mechanical, electrical or pneumatic means. The linear motion systems have gained popularity in the machine tool, semiconductor and medical industries due to the ability of the linear motion system to move loads in a linear direction to a position with extreme accuracy and at very high speed. However, problems arise with moving a stage to a specific position with high precision, while holding the position of the stage so that forces acting on the carriage will not move the carriage from the desired position. A locking system such as a brake is conventionally employed to hold the position of the stage, but conventional brake devices do not provide stability without high distortion for very high precision motion, such as that necessary in the semiconductor industry.
The linear motion system is subjected to noise during normal operation. The noise can be electrical noise, ambient noise, ground noise, transmitted noises from the linear motion systems and other noise that cause small amounts of jittering or jumping in the stage when the stage is stopped and held in a desired position. These types of jittering and jumping cannot be measured or compensated for utilizing typical feedback elements of the stage. Furthermore, when a linear motor is utilized to move the stage, the stage is subjected to a load from the driving of the servo motor or the like. The loaded stage also contributes to the jittering or jumping of the stage when the stage is held in a desired position. A conventional brake system includes an actuator coupled to a spring using a fulcrum and lever. However, this type of conventional brake system cannot control the amount of jump or jitter of the stage.
Accordingly, it is desirable to provide a system and/or method that can provide high precision motion with high stability.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The present invention relates to a stability brake for a motion system and a method of producing and using a stability brake. The stability brake includes a motor coupled to a flexure plate through a translation system. The translation system translates horizontal motion of the motor into vertical motion. The translation system translates vertical motion into a multiple of the horizontal motion. Therefore, a large vertical movement of the flexure plate can be provided by small horizontal movement of the motor, such that a translation gain results. The stability brake can be mounted to a stage in a motion system, such as a linear motion system. The stability brake is operative to absorb jitters and vibrations of the stage when the stage is moved to a working position in a motion system and held under servo at the working position.
In one aspect of the invention, the translation system is comprised of a first wedge portion and a second wedge portion. The first wedge portion is coupled to a motor through a movable strip, while the second wedge portion is coupled to a flexure plate. Horizontal movement of the movable strip by the motor causes horizontal movement of the first wedge portion which is translated into vertical movement of the second wedge portion and the flexure plate. The angles of the first and second wedge portions can be selected to provide different translation ratios (e.g., 10:1, 5:1, 3:1, 2:1), such that movement of the motor translates to movement of the flexure plate that is a multiple of the movement of the motor. The flexure plate absorbs jittering, vibration and other parasitic motions of the stage under servo.
The following description and the annexed drawings set forth in detail certain illustrative aspects of the invention. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.